all: update build constraints to Go 1.17

Do it all at once in preparation for Go 1.18 support.

To make this commit, I've simply modified the `fmt-check` Makefile
target to rewrite files instead of listing the differences. So this is a
fully mechanical change, it should not have introduced any errors.

src/runtime/wait_other.go

@@ -1,5 +1,5 @@
-// +build !tinygo.riscv
-// +build !cortexm
+//go:build !tinygo.riscv && !cortexm
+// +build !tinygo.riscv,!cortexm
 
 package runtime